Earthing and short-circuiting device
An earthing and short-circuiting device (EuK) is an electrotechnical system component which, after it has been determined that there is no voltage, is used to earth and short-circuit an active system component on all poles (rule 4 of the five safety rules ). In the event of a fault, when the disconnected part of the system is undervoltage, the feed voltage is short-circuited and an impermissibly high contact voltage cannot arise. The upstream protective devices, such as circuit breakers and fuses , separate the system part from the feed source.
In the new federal states, a distinction is made between a job that is ready to be reported and ready to be released: If only the switching points are earthed and short-circuited, the released part of the system is ready to be reported. If the work site is also earthed and short-circuited, this part of the system is "ready for release".
Executions
- permanently installed EuKs
Are closed and opened remotely using a motor or manually using a hand crank, e.g. B. the ground isolator of a high-voltage switchgear outlet or an overhead line as shown in the adjacent figure
- Insert-EuKs
Are used as earthing and short-circuiting units in low-voltage switchgear instead of the feed circuit breaker (retracted)
- rope-shaped EuKs (working earths)
Like the earthing rod or the earthing whip , EuKs are first manually connected to the earth potential and then connected to active electrotechnical system components
- Multipole EuKs
Are used for disconnection in three-phase systems , e.g. B. of medium voltage transformers .
safety instructions
EuKs must be dimensioned according to the local electrical design data, as they are supposed to safely hold the greatest possible earth and short-circuit current. No dangerous contact voltage may occur. In order to detect damage, rope-shaped EuKs are equipped with transparent insulation. Some EuKs are regularly checked for their resistance.
In the event of a short circuit, rope-shaped EuKs deflect due to the Lorentz force . Therefore, rope-shaped EuKs must not be chosen to be unnecessarily long and only be adequately fastened with the device suitable for the conductor (flat, round, rail, conductor cable, etc.).
As a special case of the five safety rules, point 3 (determining the absence of voltage), the following applies: If short-circuit-proof high-speed earth electrodes are used (spring-controlled earthing disconnectors in switchgear), actuation of the earth electrode is deemed to be "determining the absence of voltage", but this should normally not be done or only in exceptional cases.
Web links
- Video of an incorrectly installed EuK.
literature
- Gerhard Herold: Basics of electrical energy supply . Springer, 1997, ISBN 978-3-322-87190-9 , Chapter 1.3 - Electrical power supply networks.